1. Field Of The Invention
This invention relates to a device for removing a quantity of a liquid substance, such as an allergenic agent, from a storage vessel and transferring said quantity of liquid to an application structure that is used to apply the allergenic agent to the skin.
2. Description of Prior Art
Application of a fixed, or consistent, quantity of an allergenic agent to an area of a patient's skin to evaluate the reactivity of the patient to the agent has long been a problem in allergy skin testing.
Devices for simultaneously applying a plurality of allergenic agents in liquid form to the human skin are known and are currently commercially available and used. One such device is disclosed in U.S. Pat. No. 3,556,080. The device disclosed in this patent has a plurality of antigen application heads. Each of the heads is engaged to a relatively rigid handle by a separate connective arm, and the arrangement is such as to enable all of the heads to simultaneously scarify, or penetrate, a separate area of skin on a non-planar portion of the body, such as on a patient's arm, leg or back. By placement of a different liquid allergenic agent on each head of the device of U.S. Pat. No. 3,556,080, the physician, or his technician, has available an instrument for simultaneously applying different allergenic materials, or concentrations of allergenic materials to multiple skin sites on the patient. The liquid allergenic agent is normally stored in small vials, and it is desirable that a proper amount of liquid allergenic agent be transferred from its storage vial to the scarifying head of the scarifying instrument.
Loading of a correct quantity of an allergenic agent on the cluster of scarifier or skin penetrating points of the heads of said instrument is important to obtain an accurate indication of the presence or absence of reactivity by the person being tested, and also to prevent waste of expensive allergenic agents.
Prior art constructions for loading a liquid agent onto multiple points of a scarifier head are disclosed in U.S. Pat. Nos. 3,325,059; 3,366,278; 3,369,708; 3,413,975; 3,465,717; and 3,552,605. These patents show use of devices purportedly for controllably applying a fixed amount of a liquid test substance to an application head, or by loading liquid by immersing the scarifying points of the head in a pool of the liquid substance. Such prior art constructions have not been widely adopted, because of lack of control insuring uniformity of transfer of a precise amount of liquid to the scarifying head.
Other approaches to the loading of the heads of the multiple test head applicator have included: using solid glass transfer rods which are dipped into a solution that includes the antigenic material and then deposit the liquid carried on the outside of the rod onto the points of a scarifier head; and use of an eyedropper which ingests, under squeeze bulb pressure, a quantity of liquid into a tubular glass sleeve for later discharge onto the points of the scarifier head. The liquid used as the antigen carrier is generally a mixture of 50% water and 50% glycerin.
With respect to the loading of the heads of the multiple test head applicator disclosed in the U.S. Pat. No. 3,556,080, various applicators have been tested. Solid glass rods having rounded ends and solid glass rods having bulbous enlargements formed on the application end have been found to transfer inconsistent quantities of liquid due to the varying degree to which they are immersed within the liquid and the inconsistent quantity of liquid which is withdrawn or "cleaned" from the rod when the rod contacts the side or mouth of the storage vessel.
Similarly, conventional dropper-type transfer devices provide inconsistent quantities as the quantity of substance transferred is dependent upon the amount of depression or "squeeze" of the rubber bulb of the stopper both when loading the stopper from the storage vessel and when unloading the stopper onto the test head.
Such devices, and approaches to the problem, have been found to be lacking precision because they are dependent upon the subjective judgment of the person using them and are prone to inconsistent cleaning or removal of some of the substance when intentionally or inadvertently placed in contact with other objects. Also, inconsistency promoting actions such as tapping the rod or stopper with a finger or abrupt up and down motions are often required to effect transfer of the substance from the device to the test head. All of these disadvantages make proper loading of a test head with a correct and consistent quantity of a liquid, that carries an allergenic agent, difficult, if not impossible, to attain.